How worldwide changes in biological diversity affect ecosystem properties and service provision is an urgent, but still unresolved, question in ecology. Streams have been successful model systems to assess diversity-ecosystem function relationships. In particular, stream ecology has provided conclusive insight into how consumer diversity affects resource capture efficiency. Yet, we feel that ecologists have under-exploited the potential of using streams for furthering recent conceptual advances. Notably, stream ecology forms an excellent framework for promoting greater ecological realism in biodiversity-ecosystem function research and ultimately for increasing its relevance for conservation. This can be achieved by conducting observational studies of human-altered streams and manipulative experiments in real streams or artificial channels connected to natural systems. Openness is a key feature of ecological systems that drives the structural and functional response of stream communities to changed biodiversity. Moreover, incorporating trophic complexity and functional traits into further studies should lead to a better mechanistic understanding of ecosystems’ responses to realistic scenarios of species loss/invasion. Lastly, efforts should be made to evaluate simultaneously multiple facets of ecosystem functioning, with particular emphasis on key ecosystem properties behind the insurance effect of biodiversity and measures of ecosystem services.